Method of conserving energy in the treatment of wells



QLHHUH nuu Nov. 28, 1967 F. H. BRAUNLICH JR, ET AL 3,354,960

METHOD OF CONSERVING ENERGY IN THE TREATMENT OF WELLS Filed June 23, 1965 4 Sheets-Sheet l INVENTORS.

Frank H. 6/"0un//'c/7,dr: Char/es LLunsfor Nov. 28, 1967 F. H. BRAUNLICH, JR.. ET AL 3,354,950

METHOD OF CONSERVING ENERGY IN THE TREATMENT OF WELLS Filed June 23, 1965 4 Sheets-Sheet 2 l/Z IHIL Brine INVENTQRS. Frank h. Braun //c/7, Jr. BY 6/7 ar/es Z. Z ans/bro ATTORNEY Nov. 28, 1967 F. H. BRAUNLICH, JR, ET AL 3,354,960

METHOD OF CONSERVING ENERGY IN THE TREATMENT OF WELLS 4 Sheets-Sheet 5 Filed June 23, 1965 C/osea I I l 2HIFJ- I INN. r-

INVENTORS.

BY Char/es L. L unsf'o Nov. 28, 1967 F. H. BRAUNLICH, JR., ET AL 3,354,960

METHOD OF CONSERVING ENERGY IN THE TREATMENT OF WELLS pen 5r/ne 0// 113/. 9 fqda INVENTORS. Fran h. firaun/fa/ /n Char/ezs L. A uqs/bra fiTTORNE) United States Patent 3,354,960 METHOD OF CGNSERVING ENERGY BI THE TREATMENT OF WELLS;

Frank H. Braunlich, In, and Charles L. Lunsford', Tulsa,

Okla., assignors to The Dow Chemical fiornpany, Midlaud, Mich, a corporation of Delaware Filed June 23, 1965, Ser. No. 466,397 14 tClaims. (Cl. 16642) ABSTRACT OF THE DHSCLQSURE An improved method of treating a geologic formation (wherein a treating liquid is required to be forced back into the formation) which comprises injecting a gas, which is preferably preceded by at least part of the treating liquid, down a wellbore and promptly following the gas with a liquid under pressure preferably treating liquid (such liquid being required to be the treating liquid unless treating liquid were first put into the wellbore below the gas, as preferred), closing off the wellbore under pressure, whereby the gas rises through the liquid injected above it, thereby providing extended contact of the treating liquid and the formation without need for pumping equipment to remain in operation.

The invention pertains to the treatment of a subterranean formation penetrated by the wellbore of a well whereby energy expended in injecting fluids down the well may be gradually advantageously used over a desirably long time during the treatment.

The invention is based upon the discovery that an improved method of treating subterranean formations is realized by first injecting a gas (which is preferably preceded by at least part of a treating liquid to be forced back into such formation) down a wellbore and promptly following the gas with a liquid under pressure which may be more of the treating liquid or another liquid of equal or greater density, and closing off the well under pressure thereby to provide an extended period of contact of the formation with a treating liquid under pressure and thereby permits the pressuring pumps used to inject the fluids to be removed from the location immediately after injection.

In the treatment of a fluid-bearing formation penetrated by a wellbore, often referred to simply as a treatment of a well, the formation is subjected to treatment by a chemical composition, explosive, or liquid exerting hydraulic pressure, and includes, in a broad sense, as used herein, the necessary steps in reworking or repairing a well, moving packers, perforating casing, drilling, and in cementing off a well. In the treatment of a well, a fluid of some sort is invariably injected or circulated down the well and into contact, to a more-or-less extent, with the formation. The fluid must be subjected to pressure, commensurate with the job to be done. In some instances, e.g., in acidizing certain limestone or certain dolomitic formations, a satisfactory treatment requires that the aqueous acidic composition employed for that purpose be maintained under pressure in contact with the formation for an appreciable length of time. In matrix acidizing, i.e. acidizing at less than fracturing pressure, it is often desirable that the composition employed in the treatment be maintained under a moderate but steady pressure for an appreciable length of time which may extend for from a few hours or less to 24 hours or more. Treatments in such instances, conducted by heretofore known methods, require that the pumping equipment and operating personnel be kept on the job throughout this rather long period to maintain pressure on the injected fluid.

It is the principal object of the invention to provide a way of maintaining pressure on a formation by fluids injected down a well penetrating the formation for an appreciable length of time without maintaining the injection equipment on the job and to attain an advantage based upon more eflicient use of the energy of the fluids. How this and related objects are attained is made clear in the ensuing description and is defined in the appended claims.

By the practice of the invention a treating fluid can be injected down a Well in a relatively short time, say 0.5 to 2 hours, the equipment then removed, and pressure allowed to remain against the formation for as long as 12 hours and often 18 to 24 hours or longer, depending on specific conditions, particularly the character of the formation, diameter and depth of the wellbore, and nature of liquids employed. Cost benefits are also derived from the practice of the invention because, in general, it requires less fluid than is required by conventional treating methods and ei'fectuates a saving in equipment and power that otherwise would be necessary to provide the desired continued pressure on the well.

The invention is an improved method of treating a formation penetrated by a wellbore, which may or may not be cased and/or provided with tubing, which comprises (1) spotting or locating a treating liquid in the wellbore at the stratum, zone, or level of the formation to be treated; (2) locating in the wellbore, above the treating liquid, a gas which is substantially inactive with the treatment liquids or with the formation fluids, in an amount sufficient to maintain gas and liquid phases at the conditions existing at any level of the wellbore; (3) locating a displacing or weighting liquid in the wellbore above the gas in an amount sufiicient to fill the wellbore; (4) closing the wellbore at the surf-ace for a period sufficiently long to permit the gas to migrate upwardly through the displacing liquid to the top of the wellbore.

The amount of treating liquid employed should be that required for adequate treatment. In other words, the amount should be substantially that which it is calculated will be subsequently forced into the zone being treated. After location of the treating liquid in the wellbore, there must remain suflicient space in the wellbore for both the gas and subsequently located weighting liquid.

The preferred embodiment of the invention requires that the formation to be treated be provided with a casing (suitably perforated at the level to be treated) and a tubing more-or-less centrally positioned in the casing and that a first or filling liquid be injected prior to injecting the treating liquid. (No packer is needed to be used unless one is necessary between a surface casing string and easing.) Control valves are provided at ground level for each of the annulus and tubing. This embodiment presents two alternative modes of practice: one wherein injection is down the tubing and the other wherein injection is down the annulus. (When injecting down the annulus, the tubing at ground level is open or when injecting down the tubing the annulus is open at ground level.) The tubing and the annulus may be considered separate passageways or conduits. The one down which the fluids are injected may be designated as the injection conduit. It is necessary that the treating liquid, after being located in the wellbore, have access to the formation as through perforations in the casing or below the casing. Such ernbodiments comprises (1) injecting down, either the tubing or the annulus between the tubing and easing, the filling liquid in an amount at least equal to or greater than the volume of the annulus (when injected down the tubing) or at least equal to or greater than the volume of the tubing (when injected down the annulus); (2) injecting a substantially chemically unreactive gas, down the same conduit down which the filling liquid was injected, in an amount sufficient to insure both a gas phase and a liquid phase in the wellbore; (3) injecting a treating liquid, egg.

an acidizing or fracturing liquid, down the same conduit (as that down which the filling liquid and gas were injected) so as to locate or spot the treating liquid opposite the level to be treated, a portion of which must necessarily have access to the perforations in the casing, the treating liquid being used in an amount such that the volume thereof, when taken together with the volume of the filling liquid first injected, and the gas under pressure, will not be substantially greater than the volume of the annulus (when injected down the tubing) or substantially greater than the volume of the tubing (when injected down the annulus); (4) injecting down the same conduit a displacing or weighting liquid thereby forcing the filling liquid, the gas, and the treating liquid in succession upwardly into the annulus (when injection is down the tubing) or upwardly into the tubing (when injection is down the annulus) until one conduit is occupied by the filling liquid, the gas therebelow and the treating liquid, the last necessarily being below the gas, and in direct contact with the formation and the other conduit is filled with displacing liquid; capping or closing off the wellbore, i.e. both annulus and tubing, at the earths surface, for a time sufiicient to permit the injected gas to rise gradually to the top of the wellbore.

Both valves controlling flow into or from the tubing and annulus are maintained open during the injection of fluids until at least all of the gas and enough of the treating liquid have been forced (from the conduit into which it is being injected) into the other conduit to permit the outlet valve (e.g. that of the annulus when injection is down the tubing) to be closed and pressure continued on the injected fluid to compress the gas to admit substantially all of the remaining treating fluid. At the time of closing off the well (i.e. closing both annulus and tubing), when injection was down the tubing, the relative positions of the fluids, from the bottom up, are: treating liquid, gas, and filling liquid. The tubing is full of displacing liquid.

After closing the well, the gas continues to rise until it comes to rest above the liquids in the wellbore, such rise being accompanied by increased pressure exerted on the formation in the lower part of the borehole at the level being treated.

The increase in pressure of the liquid in the wellbore at the level of the formation being treated results in liquid being forced into the formation as the gas rises. The ratio of movement of liquid into the formation is slow, being at about the same rate as the rise of the gas up the wellbore. Consequently an extended period of movement of the treating liquid into the formation is accomplished.

FIGURES 1 and 2 of the annexed drawing represent a laboratory apparatus used to demonstrate the principle applied in the invention by showing two stages of progress of gas and liquid used in accordance therewith.

FIGURES 3 to 9 of the drawing are schematic sketches of a well at various stages of treatment according to the invention. FIGURE 10 shows the well, after its return to production, following treatment.

An alternative mode of practicing the embodiment of the invention, wherein the well being treated is equipped with casing and tubing, as earlier described, consists of closing off, at ground level only, the annulus or tubing being filled from below (i.e. not the one into which the liquids are being directly injected) in step (5) above and continuinng, for an additional time, to inject weighting liquid until a pressure appreciably greater than that provided by the combined effect of the gas as injected therein and the hydrostatic pressure of the liquid is provided and then shutting in the well entirely, i.e. closing off the tubing or annulus, down which the injection was made, at ground level.

It is apparent that a well may be treated according to the invention wherein a packer is employed between the tubing and casing. However such treatment, employing a closed or a set packer, would be comparable to treating an open hole or cased hole which did not have a tubing except that injections would be down the smaller tubing (as the single conduit or passageway) instead of down the larger hole or casing.

It is recommended that the well remain closed in for at least 8 or 10 hours and, in a number of instances, for a longer period of time, dependent upon the time required for the gas to rise completely to the top of the liquids in the wellbore.

The treating liquids employed in the practice of the invention may be any aqueous or organic liquid or emulsions thereof which may also contain any of the known treating materials found beneficial when brought intg contact with a fluid-bearing formation. An acidizing liquid, e.g. a 3 to 30% by weight aqueous solution of HCl, usually containing an inhibitor to acid attack on metal, illustrative.

The gas employed may be a hydrocarbon gas, e.g., natural or artificial cooking or illuminating gases, comprising various mixtures thereof of which methane, butane, ethane, propane, and the like are illustrative; any of the chemically inert gases, e.g., helium or argon; air when corrosivity or combustion due to oxygen is unlikely; nitrogen; carbon dioxide; or mixtures of these and other gases which do not react chemically to an objectionable extent with other fluids present during treatment. It is desirable that the gas employed be not highly soluble in the liquids employed, e.g. CO in aqueous liquids or hydrocarbon gases in oils, but relatively high solubility does not prevent their usage, it being necessary, however, that sufficient gas be provided over and above that which dissolves to insure that both a liquid and gas phase exist in the well. Nitrogen is the preferred gas to employ with any of the usual liquids employed in well treatments. A volume of gas, when fully expanded at the top of the wellbore, should be substantially equal to the volume formerly occupied by the gas at the bottom of the wellbore plus the volume of the treating liquid employed. The amount of gas may be readily calculated from published data and will vary somewhat, dependent upon such factors as the type of gas being used, its solubility in the liquids being used, and the conditions of temperature and pressure.

In FIGURES 1 and 2 of the drawing there are shown in each figure: chamber 2, provided with valve-controlled port 4, and filled with a liquid; valve-controlled pipe 6 providing communication between chamber 2 and chamber 8 vertically positioned below chamber 2 which contains a measured volume, at the existing pressure, of a substantially chemically unreactive gas and also a small amount of a liquid of the nature of that in chamber 2; pipe 10 leading from the lower part of chamber 8 and providing communication with vertical, relatively smalldiameter tube 12 which is about sixty inches high, open at the top, and filled to a measured height with a liquid of the nature of that in chamber 2.

Employing the apparatus of FIGURES 1 and 2, the experiment demonstrating the efficacy of the method of the invention was carried out as follows:

The system was filled with air. Any one of a number of other gases is acceptable. The valve in pipe 6 was closed and the valve in port 4 was opened. Water was poured into chamber 2 until it was completely filled. Water was then poured into tube 12, a portion of which flowed through pipe 10 into chamber 8, until tube 12 was nearly filled. The air that had originally been in the entire system was now compressed in the upper part of chamber 8. This stage is represented in FIGURE 1.

The valve in port 4 was then closed and the valve in tube 6 was opened. At this point the volume of air in the upper part of chamber 8 measured 228 cubic inches and the height of the water in tube 12 measured exactly fifty inches. The gas gradually moved upwardly from chamber 8, through the water in chamber 2 until it came to rest in the upper part of chamber 2 and, concurrently with the movement of the gas, the water rose 4% inches in tube 12 to a final height of 54% inches. The final volume of gas in chamber 2 measured 236 cubic centi- A study of the above descriptive material in reference meters, Thi stage i shown i FIGURE 2, to FIGURES 3 to 10, depicting the progress of the treat- The rise in the liquid level in tube 12, while port 4 ment being carried out in accordance with the invention, was closed, is due to an increase in pressure in the liquid clearly shows the gradual inversion of the gas, e.g., nitroat the bottom of the column of liquid in tube 12. Pipe 5 g and the fluid, e.g., brine, present in the well, resulting is representative of the point of entrance of a treating n an increase in pressure at the production one being li id f om a llb f ti f a casing) treated and in the liquid treating composition, e.g. aqueous into a formation being treated. The additional pressure HCl, being forced back into the zone of treatment. at pipe 10, which resulted in the rise of the liquid level in The following example is illustrative of a mode of the demonstration, would occur at the treatment of a zone to practicing the invention: a well, having a depth somewhat of a formation being treated according to the invention in excess of 10,000 feet and a bottom hole temperature of 'and would gradually force additional treating liquid back ut 200 F. and p n t a i g a Sandstone Oil-beating ihte the f r ati formation at a 10,000-foot level, is to be slowly treated In each of FIGURES 3 to 10, there is shown subterwith 11000321110 of a mixed aqheohs solution Ct ranean formation 13 having oil-producing zone 14 pene- 15 hydrochloric and 3% y fl c acids containing .an

trated by a wellbore which is provided with outer or surlhhlhltor: ee arsenic, nitrogen eemphllhds face String 15 and easing packer 18 positioned in the known to inhibit corrosion of metal. The well is cased annulus between the surface string and the casing near Wlth a 51/2-1heh g having perforations at the 10,000- the earths surface; cement 20 securing the surface string foot level t g ding to a point just below in place near the surface and Sealing Off the casing and 20 the perforations in the casing. The bottom end of the securing it in place at its lower end; tubing 24 terminating caslhg Cemented in P ion, forming a seal between at perforations 25 in the casing; tightly fitting cap 26 to the eesthg e the face of e fo mation.

provide sealing means for casing; pipe and valve assem- The tuhlhg and annular space between the tubing and blies 28 and 30 suitably attached independently to each of easing are filled With hrihe having a specific gravity of the tubing and the annulus formed between the tubing 25 1.10. About 6030 cubic feet (at standard conditions of and easing respectively, through Openings in the cap. temperature and pressure) of nitrogen gas are injected FIGURE 3 shows the tubing and the annulus between down the tubing to provide gas in excess of that amount the tubing and easing Substantially n with 15% c which dissolves in the brine and ensuing acid, which will brine, representing conditions at the beginning of a treat- Produce a bubble of g a t top of the annulus at the mehtin accordance i the hwehtioth 30 end of the treatment. The amount of gas employed is FIGURE 4 shows nitrogen gas (N), aqueous acidic calchlated t be shtheteht to p uP011 rising above treating liquid (HCl), for the purpose of acidizing th the liquid in the wellbore, to a volume which is greater formation, and the first portion of crude oil (oil) as a disthan its m at the bOttOm 0f the well by an amount placing liquid being successively injected through assemuhstflhtlahy equal to the Volume of treating q hly 28 down tubing 24 Brine is being displaced from the in this example, its volume is calculated to increase by annulus through assembly 30 at ground level. about 1,000 gallons. The aqueous solution of HCl and FIGURE 5 shows the stage after sufficient oil has been E containing an inhibitor to metal corrosion, -g. an injected to displace all the nitrogen gas and a substantial smlhe tYP as described in US. Patent 1,877,504 to Gr b portion of the aqueous I-ICl solution from the tubing into et 1s injected i the W ll following the gas. Oil, e.g. the annulus, and shows the brine continuing to be dislease crude Oil, as a displacing liquid is then injected Placed f o the annulus through pipe assembly 30 down the well, forcing the brine filling liquid, followed FIGURE 6 shows the continued injection of the disby the nitrogen g and h n by the aqueous W placing oil down tubing 24 whereby all the aqueous HCl down the tubing and then p the 21111111" 3 Pettieh of solution is forced into the annulus and the space below the brine t g liquid in the well flows out the tubing 24, thereby displacing additional brine out through t surface The filling q and acidic assembly 30, from the ann lu solution are located in the annulus in inverse position to At i point the valve in e a h i f that in the tubing. Some of the acidic solution remains the annulus e i closed It is recommended at the bottom of the wellbore opposite the perforations.

'ec some additional displacing oil to insure that all The displacing fins the tubing hut dees not enter th h aqueous 01 has been forced into h 1 A annulus. The outlet from the annulus and the inlet to the preferred practice, as aforesaid, is to close the valve in tuhlhg at ground level a th n closed. The well is left pipe assembly 36 while acalculated portion of the treating thu s elesed in for from about 3 to 12 hours, during liquid7 he the c Solution remains in the tubing and which time the increasing pressure at the bottom of the then to force substantially all of it from the tubing by r holeho'le tomes the aeitd treating liquid back iIltO t compressing the nitrogen gas; this provides increased formstloh as the gas rlses t0 the of the annuluspressure on the formation. FIGURE 7 shows the comple- Thereafter the tubing is P on a p py displacing tion of the injection of the displacing oil into tubing 24. 011 remaining therein, i pumped out with Oi1 being Following this step, the valve in assembly 28, leading produced- The nitrogen gas and brine y remain in the into the tubing at the ground level, is also closed. annulus- FIGURE 8 shows the gradual inversion of the nitrogen In the illustrations and in the example set forth, the gas and the brine in the annulus which is accompanied formation has been treated y y 3 Well h h Was by an increase in pressure on h HQ treating li full cased and perforated at the level being treated and below, whereby it is gradually forced into the formation. Provided With a tllhihg- However, the Practice f the Bubbles of nitrogen gas are shown rising through the brine invention is not limited to eased Wells but y he cellhi h h d i d i h 1 ducted in wells which are open hole, i.e., wherein the cas- FIGURE 9 shows the complete inversion of the nitroing terminates at a point in the hole above the formation to gen gas d h b i i th annulus, ith a ti d be treated, and the hole at the production level of the pressure diff ential on h aqueous Hcl t ti 1i nid formation to be treated is thereby open or exposed. In at h ih d i Zone whereby th aqueous HCl such instances the tubing normally extends to the procontinues t move i t th f ti ducing level or slightly below and sometimes to a point FIGURE 10 shows the well at the end or" the treatment just above the bottom of the open hole. wherein the valve to the tubing is open, the treating fluid When treating a well wherein no tubing is empolyed, has been removed, and the well is in production. Brine the order of injection is (l) treating liquid, (2) gas, and

may remain in the annulus during production. 7 (3) Weighting liquid; the well is thereafter maintained closed (as when employing a tubing) until the gas has risen to the top of the wellbore.

It is readily recignized that a treatment in accordance with the invention as shown and described provides a desirably extended treated period without the necessity of maintaining pressurizing equipment on the location, with the added advantage of having the pressure gradually increase at the zone of treatment in the formation until the gas has entirely risen to a level above the liquids present.

Having described our invention what we claim and desire to protect by Letters Patent is:

1. The method of treating a fluid-bearing zone of a subterranean formation penetrated by a wellbore Which comprises: (1) injecting down the wellbore and locating at the zone in the formation to be treated a treating liquid in an amount calculated to be that required for adequate treatment of said zone; (2) injecting down the wellbore a gas which is substantially chemically unreactive with the treating liquids and formation fluid in an amount sufficient to establish and maintain gas and liquid phases at conditions existing at any level in the wellbore; (3) injecting a weighting liquid down the wellbore, and positioning it on top of the gas, in an amount sufiicient to fill the wellbore completely to ground level; (4) closing off the wellbore at ground level for a time sufficient for the gas to rise gradually to the top of the weighting liquid to provide increased pressure in the wellbore at the zone being treated to force treating liquid back into said zone for an appreciable length of time.

2. The method according to claim 1 wherein the gas employed is selected from the class consisting of hydrocarbons of which a substantial portion is gaseous at the pressure and temperature existing at any level in the wellbore, nitrogen, air, carbon dioxide, helium, agron, xenon, and krypton.

3. The method according to claim 1 wherein the liquid treating composition employed is selected from the class consisting of organic and aqueous liquids and emulsions thereof.

4. The method according to claim 3 wherein the liquid treating composition is a 3% to 30% by weight aqueous solution of HCl.

5. The method according to claim 4 wherein said aqueous solution contains up to 5% by weight HP.

6. The method according to claim 4 wherein said aqueous solution of HCl contains an inhibitor to acidic corrosion of metal.

7. The method according to claim 1 wherein said gas is positioned on top of said treating liquid.

8. The method according to claim 1 wherein said gas is employed in an amount sufiicient to expand, upon rising above said liquid, to a volume which is greater than its volume at the bottom of the wellbore by an amount about equal to the volume of the treating liquid.

9. The method of treating a subterranean formation penetrated by a well which is provided with a tubing extending therein to a zone in the formation where treatment is desired and is more-or-less centrally positioned in the wellbore of the well to provide two concentric passageways consisting of an inner tubular passageway and an outer annular passageway which comprises: (1) injecting down one of said passageways, designated injection passageway, a space-filling liquid which is substantially chemically unreactive at the existing conditions in the well, in an amount at least equal to the volume of the other passageway; (2) injecting down the injection passageway a gas which is substantially chemically unreactive at the existing conditions in the well in an amount sufiicient to insure the presence of a gas phase and a liquid phase at the conditions existing at any level in the wellbore; (3) injecting down the injection passageway a treating liquid in an amount sufficient to provide adequate treatment of the formation; (4) injecting down the injection passageway a weighting liquid in an amount sufilcient to displace the space-filling liquid, gas, and treating liquid from said injection passageway into the other passageway and to fill all of said injection passageway; and (5) closing in the well until the gas has risen to the top of the displacing liquid whereby pressure is gradually increased at the treatment level of the wellbore thereby causing treating liquid to be gradually forced into the formation during the time the gas was rising through the liquid in the wellbore.

10. The method according to claim 9 wherein said injection passageway is the tubing.

11. The method according to claim 9 wherein said injection passageway is the annulus between the tubing and the face of the borehole wall.

12. The method according to claim 11 wherein said well is cased and said injection passageway is the annulus between the tubing and the casing.

13. The method according to claim 9 wherein the gas employed is selected from the class consisting of hydrocarbons of which a substantial portion is gaseous at the pressure and the temperature existing at any level in the wellbore, nitrogen, air, carbon dioxide, helium, argon, xenon, and krypton.

14. The method according to claim 9 wherein said other passageway is closed when the wellbore is filled and said weighting liquid is continued to be injected down said injection passageway until the injected gas is compressed sufficiently to produce a pressure in the wellbore to an extent sufiicient said treating liquid begins to start to move at a desired rate into the zone of the formation Where treatment is to oe effected.

References Cited UNITED STATES PATENTS 2,053,285 9/1936 Grebe 16642 2,802,537 8/1957 Goldinger 16642 2,885,004 5/1959 Perry l6642 3,193,010 7/1965 Bielstein 166-2l CHARLES E. OCONNELL, Primary Examiner.

NILE C. BYERS, Examiner. 

9. THE METHOD OF TREATING A SUBTERRANEAN FORMATION PENETRATED BY A WELL WHICH IS PROVIDED WITH A TUBING EXTENDING THEREIN TO A ZONE IN THE FORMATION WHERE TREATMENT IS DESIRED AND IS MORE-OR-LESS CENTRALLY POSITIONED IN THE WELLBORE OF THE WELL TO PROVIDE TWO CONCENTRIC PASSAGEWAYS CONSISTING OF AN INNER TUBULAR PASSAGEWAY AND AN OUTER ANNULAR PASSAGEWAY WHICH COMPRISES: (1) INJECTING DOWN ONE OF SAID PASSAGEWAYS, DESIGNATED INJECTION PASSAGEWAY, A SPACE-FILLING LIQUID WHICH IS SUBSTANTIALLY CHEMICALLY UNREACTIVE OF THE EXISTING CONDITIONS IN THE WELL, IN AN AMOUNT AT LEAST EQUAL TO THE VOLUME OF THE OTHER PASSAGEWAY; (2) INJECTING DOWN THE INJECTION PASSAGEWAY A GAS WHICH IS SUBSTANTIALLY CHEMICALLY UNREACTIVE AT THE EXISTING CONDITIONS IN THE WELL IN AN AMOUNT SUFFICIENT TO INSURE THE PRESENCE OF A GAS PHASE AND A LIQUID PHASE AT THE CONDITIONS EXISTING AT ANY LEVEL IN THE WELLBORE; (3) INJECTING DOWN THE INJECTION PASSAGEWAY A TREATING LIQUID IN AN AMOUNT SUFFICIENT TO PROVIDE ADEQUATE TREATMENT OF THE FORMATION; (4) INJECTION DOWN THE INJECTION PASSAGEWAY A WEIGHTING LIQUID IN AN AMOUNT SUFFICIENT TO DISPLACE THE SPACE-FILLING LIQUID, GAS, AND TREATING LIQUID FROM SAID INJECTION PASSAGEWAY INTO THE OTHER PASSAGEWAY AND TO FILL ALL OF SAID INJECTION PASSAGEWAY; AND (5) CLOSING IN THE WELL UNTIL THE GAS HAS RISEN TO THE TOP OF THE DISPLACING LIQUID WHEREBY PRESSURE IS GRADUALLY INCREASED AT THE TREATMENT LEVEL OF THE WELLBORE THEREBY CAUSING TREATING LIQUID TO BE GRADUALLY FORCED INTO THE FORMATION DURING THE TIME THE GAS WAS RISING THROUGH THE LIQUID IN THE WELLBORE. 